Field of the Disclosure
This disclosure relates generally to directional drilling methods and, in particular, to methods for navigating a formation using a closed loop system using a downhole processor without access to a surface processor.
Brief Description of the Related Art
Boreholes are usually drilled with a drill string that includes a tubular member having a drilling assembly (also referred to as the bottomhole assembly or “BHA”) with a drill bit attached to the bottom end thereof. The drill string can be navigated or steered through the formation by changing the orientation of the drill bit while drilling. In general, in order to steer the drill string, various survey measurements may be taken to provide information related to the current location and orientation of the drill bit. These measurements may be obtained using downhole sensors but generally do not provide complete information, such as a position of the drill bit within the formation, required for directional drilling. The measurements are therefore sent a processor that is at a surface location. The surface processor generally has access to this additional information and determines a steering action to be taken at the drill bit. The surface processor then sends a steering signal downhole that may be implemented at the drill bit. As boreholes becomes longer and deeper, time delays and data degradation during communication limits the suitability of this method of drilling.